I found an answer looking at the driver source code: InsertManyAsync uses BulkWriteAsync internally, so using InsertManyAsync is similar to writing:
List<BsonDocument> documents = ... collection.BulkWriteAsync(documents.Select(d => new InsertOneModel<BsonDocument>(d)));
Obviously, if all operations are inserts, InsertManyAsync should be used.
Stefano castriotta
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